Process for producing a pufa-containing biomass which has high cell stability

ABSTRACT

According to the invention, it was found that culturing of PUFA-producing cells in a content of sulphate makes it possible to obtain a biomass having high cell stability and thus PUFAs protected against oxidation in a sustained manner, which biomass can in addition be advantageously further processed into a feedstuff.

The present invention relates to a process for producing a PUFA-containing biomass having high cell stability.

Processes for producing biomass containing polyunsaturated fatty acids (PUFAs) have already been described in the prior art. A problem in the case of the biomass obtained is frequently the stability of the cell wall. The cell wall must not be too labile, since otherwise the oil present might be released too early and the unsaturated fatty acids oxidized in this connection. On the other hand, the cell wall must also not be too stable, since otherwise, during the production of the feedstuff, the cells are not completely broken and/or break-up of the cells requires a very high energy input, and so the oil cannot be completely released from the cells or only with a very high energy input and thus high costs.

It is therefore an object of the present invention to provide a process in which the biomass obtained has a cell stability which is suited to the further processing of the biomass into feedstuff and which must be neither too high nor too low.

According to the invention, it was found that, surprisingly, the stability of the cell wall can be optimized by specific addition of sulphate to the fermentation medium.

In this connection, it became apparent that an optimal cell stability can be attained by adding sulphate in an amount such that a sulphate concentration of 25 to 60 g/kg ensues in the resulting biomass.

Also, it became apparent that the biomass thus obtained can be further processed at a very low energy input into a feedstuff with high abrasion resistance and high water stability.

Furthermore, it became apparent that the feedstuff obtained using the biomass according to the invention can be used especially advantageously for farming fish.

Another object of the present invention can therefore be considered that of providing a biomass which, owing to its properties, is suited to an especially good extent to being able to be further processed into a feedstuff.

The present invention therefore firstly provides a process for producing a polyunsaturated fatty acid (PUFA)-containing biomass, characterized in that production of the biomass comprises culturing microorganisms in a fermentation medium containing sulphate in an amount such that a sulphate concentration, based on the dry mass, of 25 to 60 g/kg ensues in the resulting biomass. In this connection, the sulphate concentration in the resulting biomass is preferably 25 to 50 g/kg, in particular 25 to 40 g/kg, especially preferably 25 to 35 g/kg, based in each case on the dry mass.

The present invention similarly further provides a PUFA-containing biomass which is obtainable using a process according to the invention.

The present invention similarly provides a PUFA-containing biomass which has a sulphate content of 25 to 60 g/kg, based on the dry mass, and is obtainable preferably by a process described above. The sulphate content is preferably 25 to 50 g/kg, in particular 25 to 40 g/kg, especially preferably 25 to 35 g/kg, based in each case on the dry mass.

According to the invention, “sulphate content” is to be understood to mean the total content of sulphate, i.e. the content of free and bound, in particular organically bound, sulphate. It can be assumed that the majority of the sulphate present in the biomass is present as a constituent of exopolysaccharides, which are involved in the formation of the cell wall of microorganisms.

According to the invention, the sulphate content is preferably determined by ascertaining the sulphur content of the biomass obtained, since the majority of the sulphur present in the biomass can be attributed to the sulphate present. Sulphur which can be attributed to other sources can be disregarded owing to the amount of sulphate present. Thus, the amount of sulphate present can be readily ascertained from the amount of sulphur ascertained.

In this connection, the sulphur content of the biomass is preferably determined by elemental analysis in accordance with DIN EN ISO 11885. For the analysis of the sulphur content of the biomass, appropriate aliquots of sample are disrupted preferably with nitric acid and hydrogen peroxide at 240° C. under pressure prior to the analysis in order to ensure the free accessibility of the sulphur present.

The present invention therefore also further provides a process for producing a biomass containing polyunsaturated fatty acids (PUFAs), characterized in that production of the biomass comprises culturing microorganisms in a fermentation medium containing sulphate in an amount such that a sulphur content of 8 to 20 g/kg, based on the dry mass, can be detected in the resulting biomass by elemental analysis in accordance with DIN EN ISO 11885. In this connection, the sulphur content in the resulting biomass is preferably 8 to 17 g/kg, in particular 8 to 14 g/kg, especially preferably 8 to 12 g/kg, based in each case on the dry mass.

The present invention therefore also further provides a PUFA-containing biomass, characterized in that a sulphur content of 8 to 20 g/kg, based on the dry mass, can be detected by elemental analysis in accordance with DIN EN ISO 11885. In this connection, the sulphur content in the resulting biomass is preferably 8 to 17 g/kg, in particular 8 to 14 g/kg, especially preferably 8 to 12 g/kg, based in each case on the dry mass.

According to the invention, the phosphorus content of biomasses according to the invention is, with regard to the dry mass, preferably 1 to 6 g/kg, in particular 2 to 5 g/kg. The phosphorus content is preferably likewise ascertained by elemental analysis in accordance with DIN EN ISO 11885.

The biomass according to the invention preferably comprises cells, and preferably consists substantially of those cells which already naturally produce PUFAs; however, the cells can also be cells enabled by appropriate gene technology methods to produce PUFAs. In this context, the production may be autotrophic, mixotrophic or heterotrophic.

Preferably, the cells of the biomass are those which produce PUFAs heterotrophically. According to the invention, the cells preferably take the form of algae, fungi, in particular yeasts, or protists. The cells are especially preferably microbial algae or fungi.

Suitable cells of oil-producing yeasts are, in particular, strains of Yarrowia, Candida, Rhodotorula, Rhodosporidium, Cryptococcus, Trichosporon and Lipomyces.

A biomass according to the invention preferably comprises cells, and preferably consists substantially of those cells of the taxon Labyrinthulomycetes (Labyrinthulea, slime nets), in particular those of the family of the Thraustochytriaceae. The family of the Thraustochytriaceae includes the genera Althomia, Aplanochytrium, Elnia, Japonochytrium, Schizochytrium, Thraustochytrium, Aurantiochytrium, Oblongichytrium and Ulkenia. Particular preference is given to cells of the genera Thraustochytrium, Schizochytrium, Aurantiochytrium or Oblongichytrium, especially those of the genus Aurantiochytrium. A particularly preferred strain is the strain Aurantiochytrium limacinum SR21 (IFO 32693).

The biomass according to the invention preferably takes the form of the product of a fermentative culturing process. Accordingly, the biomass may contain not only the cells to be disrupted but also constituents of the fermentation medium. These constituents may take the form of, in particular, salts, antifoam agents and unreacted carbon source and/or nitrogen source. The cell content in this biomass is preferably at least 70% by weight, preferably at least 75% by weight. Optionally, the cell content in the biomass may be increased by suitable wash steps to, for example, at least 80 or at least 90% by weight before carrying out the cell disruption process. However, the biomass obtained may also be used directly in the cell disruption process.

The cells in the biomass are preferably distinguished by the fact that they contain at least 20% by weight, preferably at least 30% by weight, in particular at least 35% by weight, of PUFAs, based in each case on the cell dry mass.

In a preferred embodiment, the majority of the lipids is present in the form of triglycerides, with preferably at least 50% by weight, in particular at least 75% by weight and, in an especially preferred embodiment, at least 90% by weight of the lipids present in the cell being present in the form of triglycerides.

Preferably, at least 10% by weight, in particular at least 20% by weight, especially preferably 20 to 60% by weight, in particular 20 to 40% by weight, of the fatty acids present in the cell are PUFAs.

According to the invention, polyunsaturated fatty acids (PUFAs) are understood to mean fatty acids having at least two C-C double bonds. According to the invention, highly unsaturated fatty acids (HUFAs) are preferred among the PUFAs. According to the invention, HUFAs are understood to mean fatty acids having at least four C-C double bonds.

The PUFAs may be present in the cell in free form or in bound form. Examples of the presence in bound form are phospholipids and esters of the PUFAs, in particular monoacyl-, diacyl-and triacylglycerides. In a preferred embodiment, the majority of the PUFAs is present in the form of triglycerides, with preferably at least 50% by weight, in particular at least 75% by weight and, in an especially preferred embodiment, at least 90% by weight of the PUFAs present in the cell being present in the form of triglycerides.

Preferred PUFAs are omega-3 fatty acids and omega-6 fatty acids, with omega-3 fatty acids being especially preferred. Preferred omega-3 fatty acids here are the eicosapentaenoic acid (EPA, 20:5ω-3), particularly the (5Z,8Z,11Z,14Z,17Z)-eicosa-5,8,11,14,17-pentaenoic acid, and the docosahexaenoic acid (DHA, 22:6ω-3), particularly the (4Z,7Z,10Z,13Z,16Z,19Z)-docosa-4,7,10,13,16,19-hexaenoic acid, with the docosahexaenoic acid being especially preferred.

Processes for producing the PUFA-containing cells especially of the order Thraustochytriales have been described in detail in the prior art (see, for example, WO91/07498, WO94/08467, WO97/37032, WO97/36996, WO01/54510). As a rule, the production takes place by cells being cultured in a fermenter in the presence of a carbon source and of a nitrogen source. In this context, biomass densities of more than 100 grams per litre and production rates of more than 0.5 gram of lipid per litre per hour may be attained. The process is preferably carried out as what is known as a fed-batch process, i.e. the carbon and nitrogen sources are fed in incrementally during the fermentation. Once the desired biomass has been obtained, lipid production may be induced by various measures, for example by limiting the nitrogen source, the carbon source or the oxygen content or combinations of these.

Suitable carbon sources are both alcoholic and non-alcoholic carbon sources. Examples of alcoholic carbon sources are methanol, ethanol and isopropanol. Examples of non-alcoholic carbon sources are fructose, glucose, sucrose, molasses, starch and corn syrup.

Suitable nitrogen sources are both inorganic and organic nitrogen sources. Examples of inorganic nitrogen sources are nitrates and ammonium salts, in particular ammonium sulphate and ammonium hydroxide. Examples of organic nitrogen sources are amino acids, in particular glutamate, and urea.

According to the invention, the desired sulphate content in the resulting biomass may be achieved in different ways.

For example, in what is known as a batch process, the required amount of sulphate may be initially charged in full right at the start. The amount of sulphate required can be easily calculated, since the cells used to form the biomass virtually completely assimilate the sulphate.

When using what is known as a fed-batch process, the amount of sulphate required may alternatively be metered in during the course of fermentation or, accordingly, some of the sulphate may be initially charged and the remainder metered in during the course of fermentation.

Especially when it emerges during the course of fermentation that the amount of biomass produced exceeds the originally calculated value, it is possible to ensure by subsequent metering-in of sulphate that the resulting biomass has sufficient cell stability.

According to the invention, the sulphate salt used is preferably sodium sulphate, ammonium sulphate or magnesium sulphate and also mixtures thereof.

During fermentation, the chloride content is, with regard to the liquid fermentation medium including the biomass present, preferably always below 3 g/kg, in particular below 1 g/kg, especially preferably below 400 mg/kg of fermentation medium.

In addition to sulphates and any chlorides used, it is also optionally possible during fermentation to use further salts, especially those selected from sodium carbonate, sodium hydrogen carbonate, soda ash or inorganic phosphorus compounds.

If further salts are used, these are preferably used in an amount such that each one during fermentation, with regard to the liquid fermentation medium including the biomass present, is present in each case in an amount of always less than 10 g/kg, in particular less than 5 g/kg, especially preferably less than 3 g/kg in the fermentation medium.

According to the invention, the total salt content in the fermentation medium including the biomass present is preferably always below 35 g/kg, in particular below 30 g/kg, during the course of the entire fermentation process. Especially preferably, the total salt content during the entire fermentation process, with regard to the liquid fermentation medium including the biomass present, is between 10 and 35 g/kg, in particular between 12 and 30 g/kg.

According to the invention, the sulphate content in the fermentation medium including the biomass present is preferably always between 5 and 16 g/kg during the course of the entire fermentation process.

In addition, organic phosphorus compounds and/or known growth-stimulating substances, such as, for example, yeast extract or corn steep liquor, may also be added to the fermentation medium so as to have a positive effect on the fermentation.

The cells are preferably fermented at a pH of 3 to 11, in particular 4 to 10, and preferably at a temperature of at least 20° C., in particular 20 to 40° C., especially preferably at least 30° C. A typical fermentation process takes up to approximately 100 hours.

According to the invention, the cells are preferably fermented up to a biomass density of at least 50, 60 or 70 g/l, in particular at least 80 or 90 g/l, especially preferably at least 100 g/l. In this case, the data are based on the content of dry biomass in relation to the total volume of the fermentation broth after the fermentation has ended. The content of dry biomass is determined by filtering-off of the biomass from the fermentation broth, subsequent washing with water, then complete drying—for example in a microwave—and lastly ascertainment of the dry weight.

After harvesting the cells or optionally even shortly before harvesting the cells, the cells are preferably pasteurized in order to kill the cells and to inactivate enzymes which might promote lipid degradation.

After the fermentation has ended, the biomass is harvested. By means of centrifugation, filtration, decanting or solvent evaporation, it is possible to remove the majority of the fermentation medium from the biomass. Solvent evaporation is preferably achieved using a drum dryer, a tunnel dryer, by means of spray drying or vacuum evaporation. In particular, solvent evaporation may also be achieved using a rotary evaporator, a thin-film evaporator or a falling-film evaporator. A useful alternative to solvent evaporation is, for example, reverse osmosis for concentrating the fermentation broth. Subsequently, the biomass obtained is optionally further dried, preferably by means of fluidized bed granulation. Preferably, the moisture content is reduced to below 15% by weight, in particular to below 10% by weight, especially preferably to below 5% by weight, by the drying process.

According to the invention, “dry mass” is accordingly preferably to be understood to mean a biomass having a moisture content of below 10% by weight, in particular below 5% by weight.

In a particularly preferred embodiment of the invention, the biomass is dried in accordance with the invention in a fluidized bed granulation process or a nozzle spray drying process, as described in EP13176661.0 for example.

During the drying process, silica may optionally be added to the biomass as anti-caking agent so that the biomass can be converted to an easier-to-manage state. For this purpose, the fermentation broth comprising biomass and also the silica are preferably sprayed into the particular drying zone. Alternatively, the biomass is preferably mixed with the silica only after the drying process. In this regard, reference is also made in particular to the patent application EP13187631.0.

In a preferred embodiment, a biomass to be used according to the invention has a concentration of silica, in particular hydrophilic or hydrophobic silica, of 0.2 to 10% by weight, in particular 0.5 to 5% by weight, especially 0.5 to 2% by weight, after the drying process.

A free-flowing, fine-grained or coarse-grained product, preferably a granulate, is preferably obtained by the drying process. A product having the desired particle size can optionally be obtained from the granulate obtained by sieving or dust separation.

Providing a free-flowing fine-grained powder was obtained, this can optionally be converted into a coarse-grained, free-flowing and largely dust-free product, which can be stored, by suitable compacting or granulating processes.

Conventional organic or inorganic auxiliaries or supports such as starch, gelatin, cellulose derivatives or similar substances, which are typically used in food processing or feed processing as binding agents, gelling agents or thickeners, may optionally be used in this subsequent granulation or compacting process.

“Free-flowing” according to the invention is understood to mean a powder that can flow out unhindered from a series of glass efflux vessels having different size outflow openings, at least from the vessel having the 5 millimetre opening (Klein: Seifen, Öle, Fette, Wachse 94, 12 (1968)).

“Fine-grained” according to the invention is understood to mean a powder having a predominant fraction (>50%) of particle sizes of 20 to 100 micrometres in diameter.

“Coarse-grained” according to the invention is understood to mean a powder having a predominant fraction (>50%) of particle sizes of 100 to 2500 micrometres in diameter.

“Dust-free” according to the invention is understood to mean a powder that contains only low fractions (<10%, preferably <5%) of particle sizes below 100 micrometres.

Particle sizes are preferably determined according to the invention by laser diffraction spectrometric methods. Possible methods are described in the textbook “Teilchengröβenmessung in der Laborpraxis” [Particle size measurement in the laboratory] by R. H. Müller and R. Schuhmann, Wssenschaftliche Verlagsgesellschaft Stuttgart (1996) and in the textbook “Introduction to Particle Technology” by M. Rhodes, Wiley & Sons (1998). Inasmuch as various methods can be used, the first-cited usable method from the textbook by R.H. Müller and R. Schuhmann for the measuring of particle size is preferably used.

The products obtained by the drying process according to the invention preferably have a fraction of at least 80% by weight, particularly at least 90% by weight, particularly preferably at least 95% by weight, of particles having a particle size of 100 to 3500 micrometres, preferably 100 to 3000 micrometres, above all 100 to 2500 micrometres.

The products of a fluidized bed granulation process obtained according to the invention preferably have in this case a fraction of at least 80% by weight, particularly at least 90% by weight, particularly preferably at least 95% by weight, of particles having a particle size of 200 to 3500 micrometres, preferably 300 to 3000 micrometres, above all 500 to 2500 micrometres.

The products of a spray drying process obtained according to the invention preferably have in contrast a fraction of at least 80% by weight, particularly at least 90% by weight, particularly preferably at least 95% by weight, of particles having a particle size of 100 to 500 micrometres, preferably 100 to 400 micrometres, above all 100 to 300 micrometres.

The products of a spray drying process and subsequent granulation process obtained according to the invention preferably have a fraction of at least 80% by weight, particularly at least 90% by weight, particularly preferably at least 95% by weight, of particles having a particle size of 100 to 1000 micrometres.

The fraction of dust, i.e. particles having a particle size of less than 100 micrometres, is preferably at most 10% by weight, particularly at most 8% by weight, particularly preferably at most 5% by weight, above all at most 3% by weight.

The bulk density of the products according to the invention is preferably from 400 to 800 kg/m³, particularly preferably from 450 to 700 kg/m³.

According to the invention, it became further apparent that a biomass according to the invention can be further processed at low energy input into a feedstuff with high oil load capacity, high abrasion resistance and high water stability.

The present invention therefore also further provides a feedstuff comprising a biomass according to the invention and also further feedstuff ingredients.

In this connection, the further feedstuff ingredients are preferably selected from protein-containing, carbohydrate-containing, nucleic-acid-containing and lipid-soluble components and, if appropriate, further fat-containing components and furthermore from among other additives such as minerals, vitamins, pigments and amino acids. Besides, structurants may also be present, besides nutrients, for example so as to improve the texture or the appearance of the feedstuff. Furthermore, it is also possible to employ, for example, binders so as to influence the consistency of the feedstuff. A component which is preferably employed and which constitutes both a nutrient and a structurant is starch.

According to the invention, a feedstuff according to the invention or a composition used to produce a feedstuff according to the invention is preferably distinguished by the fact that it contains a biomass according to the invention in an amount of 2 to 24% by weight, preferably 4 to 22% by weight, in particular 9 to 20% by weight, above all 11 to 18% by weight.

Said feedstuff or the composition used to produce the feedstuff preferably additionally has at least one, preferably all, of the following properties:

-   -   a) a total protein content of 33 to 67% by weight, preferably 39         to 61% by weight, in particular 44 to 55% by weight;     -   b) a total fat content of 5 to 25% by weight, preferably 8 to         22% by weight, in particular 10 to 20% by weight, above all 12         to 18% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 6 to 17% by weight,         especially preferably 8 to 14% by weight;     -   d) a polyunsaturated fatty acid (PUFA) content of 2 to 13% by         weight, preferably 3 to 11% by weight, in particular 4 to 10% by         weight, above all 5.5 to 9% by weight;     -   e) an omega-3 fatty acid content of 1 to 7% by weight,         preferably 1.5 to 5.5% by weight, in particular 2 to 5% by         weight, above all 2.5 to 4.5% by weight;     -   f) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.8%         by weight, in particular 1 to 2.8% by weight, above all 1.3 to         2.4% by weight, in particular 1.3 to 2.2% by weight.

The invention therefore preferably also provides a feedstuff or a composition suitable for producing the feedstuff having at least one, preferably all, of the following properties:

-   -   a) a total protein content of 33 to 67% by weight, preferably 39         to 61% by weight, in particular 44 to 55% by weight;     -   b) a total fat content of 5 to 25% by weight, preferably 8 to         22% by weight, in particular 10 to 20% by weight, above all 12         to 18% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 6 to 17% by weight,         especially preferably 8 to 14% by weight;     -   d) a polyunsaturated fatty acid (PUFA) content of 2 to 13% by         weight, preferably 3 to 11% by weight, in particular 4 to 10% by         weight, above all 5.5 to 9% by weight;     -   e) an omega-3 fatty acid content of 1 to 7% by weight,         preferably 1.5 to 5.5% by weight, in particular 2 to 5% by         weight, above all 2.5 to 4.5% by weight;     -   f) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.8%         by weight, in particular 1 to 2.8% by weight, above all 1.3 to         2.4% by weight, in particular 1.3 to 2.2% by weight.

The invention therefore preferably also provides a feedstuff or a composition suitable for producing the feedstuff having at least one, preferably all, of the following properties:

-   -   a) a total protein content of 33 to 67% by weight, preferably 39         to 61% by weight, in particular 44 to 55% by weight;     -   b) a total fat content of 5 to 25% by weight, preferably 8 to         22% by weight, in particular 10 to 20% by weight, above all 12         to 18% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 6 to 17% by weight,         especially preferably 8 to 14% by weight;     -   d) a content of biomass according to the invention, in         particular a Labyrinthulea biomass according to the invention,         preferably a Thraustochytriaceae biomass according to the         invention, of 2 to 24% by weight, preferably 4 to 22% by weight,         in particular 9 to 20% by weight, above all 11 to 18% by weight;     -   e) a polyunsaturated fatty acid (PUFA) content of 2 to 13% by         weight, preferably 3 to 11% by weight, in particular 4 to 10% by         weight, above all 5.5 to 9% by weight;     -   f) an omega-3 fatty acid content of 1 to 7% by weight,         preferably 1.5 to 5.5% by weight, in particular 2 to 5% by         weight, above all 2.5 to 4.5% by weight;     -   g) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.8%         by weight, in particular 1 to 2.8% by weight, above all 1.3 to         2.4% by weight, in particular 1.3 to 2.2% by weight.

The invention therefore preferably also provides a feedstuff or a composition suitable for producing the feedstuff having at least one, preferably all, of the following properties:

-   -   a) a total protein content of 33 to 67% by weight, preferably 39         to 61% by weight, in particular 40 to 50% by weight;     -   b) a total fat content of 5 to 25% by weight, preferably 8 to         22% by weight, in particular 10 to 20% by weight, above all 12         to 18% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 6 to 17% by weight,         especially preferably 8 to 14% by weight;     -   d) a content of an Aurantiochytrium biomass according to the         invention, preferably an Aurantiochytrium limacinum biomass         according to the invention, above all an Aurantiochytrium         limacinum SR21 biomass according to the invention, of 2 to 24%         by weight, preferably 4 to 22% by weight, in particular 9 to 20%         by weight, above all 11 to 18% by weight;     -   e) a polyunsaturated fatty acid (PUFA) content of 2 to 13% by         weight, preferably 3 to 11% by weight, in particular 4 to 10% by         weight, above all 5.5 to 9% by weight;     -   f) an omega-3 fatty acid content of 1 to 7% by weight,         preferably 1.5 to 5.5% by weight, in particular 2 to 5% by         weight, above all 2.5 to 4.5% by weight;     -   g) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.8%         by weight, in particular 1 to 2.8% by weight, above all 1.3 to         2.4% by weight, in particular 1.3 to 2.2% by weight.

By extrusion of the above-mentioned compositions, it is possible to obtain an extrudate having an abrasion resistance of at least 91%, in particular at least 92, 93 or 94%. The present invention preferably provides said extrudates.

According to the invention, abrasion resistance was determined as follows: The dried extrudate (having a diameter of 4 mm and a length of 4 mm) was exposed to a mechanical load using the Holmen pellet tester NHP100 (Borregaard Lignotech, Hull, UK). Before carrying out the test, the samples were screened in order to remove any adherent fine particles. The processed samples (100 g) were subsequently introduced into the pellet tester using a 2.5 mm filter screen. The pellets were subsequently conveyed through a pipe having right-angled pipe bends at high air velocity (about 70 mbar) for 30 seconds. The experimental parameters are predetermined by the equipment. Subsequently, abrasion was determined by weighing. Abrasion resistance was specified as PDI (Pellet Durability Index), defined as the amount in per cent of sample remaining in the filter screen after the test has been carried out. The test was carried out with three samples and then the mean was determined.

It proved to be especially advantageous according to the invention when the extrusion is done at an energy input of 12-28 Wh/kg, in particular 14-26 Wh/kg, especially preferably 16-24 Wh/kg, above all 18-22 Wh/kg.

In this connection, a screw or twin-screw extruder is preferably employed in the extrusion process. The extrusion process is preferably carried out at a temperature of 80-220° C., in particular 80-130° C., above all 95-110° C., a pressure of 10-40 bar, and a shaft rotational speed of 100-1000 rpm, in particular 300-700 rpm. The residence time of the mixture introduced is preferably 5-30 seconds, in particular 10-20 seconds.

The extrusion process may optionally comprise a compacting step and/or a compression step.

It is preferred to intimately mix the components with each other before carrying out the extrusion process. This is preferably carried out in a drum equipped with vanes. In a preferred embodiment, this mixing step includes an injection of steam, in particular so as to bring about swelling of the starch which is preferably present. In this case, the injection of steam is carried out preferably at a pressure of 1 to 5 bar, especially preferably at a pressure of 2 to 4 bar.

Before being mixed with the algae biomass, the further foodstuff or feedstuff ingredients are preferably comminuted—if required—so as to ensure that a homogeneous mixture is obtained in the mixing step. The comminuting of the further foodstuff or feedstuff ingredients may be carried out, for example, using a hammer mill.

The extrudate created preferably has a diameter of 1 to 14 mm, preferably 2 to 12 mm, in particular 2 to 6 mm, and preferably also has a length of 1 to 14 mm, preferably 2 to 12 mm, in particular 2 to 6 mm. The length of the extrudate is set during extrusion by using a cutting tool. The length of the extrudate is preferably selected such that it approximately corresponds to the diameter of the extrudate. The diameter of the extrudate is defined by selecting the screen diameter.

In one embodiment preferred according to the invention, the extrusion process is followed by the extrudate obtained being loaded with oil. To this end, the extrudate is preferably initially dried to a moisture content of at most 5% by weight. According to the invention, the extrusion product may be loaded with oil by, for example, placing the extrudate in oil or spraying the extrudate with oil; however, according to the invention, preference is given to vacuum coating.

In this way, feedstuffs are obtained which contain biomasses according to the invention preferably in an amount of 2 to 22% by weight, in particular 4 to 20% by weight, especially preferably 8 to 18% by weight, above all 10 to 16% by weight.

Accordingly, said feedstuffs preferably additionally have at least one, preferably all, of the following properties:

-   -   a) a total protein content of 30 to 60% by weight, preferably 35         to 55% by weight, in particular 40 to 50% by weight;     -   b) a total fat content of 15 to 35% by weight, preferably 18 to         32% by weight, in particular 20 to 30% by weight, above all 22         to 28% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 5 to 15% by weight,         especially preferably 7 to 13% by weight;     -   d) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by         weight, preferably 3 to 10% by weight, in particular 4 to 9% by         weight, above all 5 to 8% by weight;     -   e) an omega-3 fatty acid content of 1 to 6% by weight,         preferably 1.5 to 5% by weight, in particular 2 to 4.5% by         weight, above all 2.5 to 4% by weight;     -   f) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.5%         by weight, in particular 1 to 2.5% by weight, above all 1.2 to         2.2% by weight, in particular 1.2 to 2.0% by weight.

The invention therefore preferably also provides a feedstuff, in particular an extrudate, having at least one, preferably all, of the following properties:

-   -   a) a total protein content of 30 to 60% by weight, preferably 35         to 55% by weight, in particular 40 to 50% by weight;     -   b) a total fat content of 15 to 35% by weight, preferably 18 to         32% by weight, in particular 20 to 30% by weight, above all 22         to 28% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 5 to 15% by weight,         especially preferably 7 to 13% by weight;     -   d) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by         weight, preferably 3 to 10% by weight, in particular 4 to 9% by         weight, above all 5 to 8% by weight;     -   e) an omega-3 fatty acid content of 1 to 6% by weight,         preferably 1.5 to 5% by weight, in particular 2 to 4.5% by         weight, above all 2.5 to 4% by weight;     -   f) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.5%         by weight, in particular 1 to 2.5% by weight, above all 1.2 to         2.2% by weight, in particular 1.2 to 2.0% by weight.

The invention therefore preferably also provides a feedstuff, in particular an extrudate, having at least one, preferably all, of the following properties:

-   -   a) a total protein content of 30 to 60% by weight, preferably 35         to 55% by weight, in particular 40 to 50% by weight;     -   b) a total fat content of 15 to 35% by weight, preferably 18 to         32% by weight, in particular 20 to 30% by weight, above all 22         to 28% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 5 to 15% by weight,         especially preferably 7 to 13% by weight;     -   d) a content of a biomass according to the invention, in         particular a Labyrinthulea biomass according to the invention,         preferably a Thraustochytriaceae biomass according to the         invention, of 2 to 22% by weight, preferably 4 to 20% by weight,         in particular 8 to 18% by weight, above all 10 to 16% by weight;     -   e) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by         weight, preferably 3 to 10% by weight, in particular 4 to 9% by         weight, above all 5 to 8% by weight;     -   f) an omega-3 fatty acid content of 1 to 6% by weight,         preferably 1.5 to 5% by weight, in particular 2 to 4.5% by         weight, above all 2.5 to 4% by weight;     -   g) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.5%         by weight, in particular 1 to 2.5% by weight, above all 1.2 to         2.2% by weight, in particular 1.2 to 2.0% by weight.

The invention therefore preferably also provides a feedstuff, in particular an extrudate, having at least one, preferably all, of the following properties:

-   -   a) a total protein content of 30 to 60% by weight, preferably 35         to 55% by weight, in particular 40 to 50% by weight;     -   b) a total fat content of 15 to 35% by weight, preferably 18 to         32% by weight, in particular 20 to 30% by weight, above all 22         to 28% by weight;     -   c) a total starch content of at most 25% by weight, in         particular at most 20% by weight, preferably 5 to 15% by weight,         especially preferably 7 to 13% by weight;     -   h) a content of an Aurantiochytrium biomass according to the         invention, preferably an Aurantiochytrium limacinum biomass         according to the invention, above all an Aurantiochytrium         limacinum SR21 biomass according to the invention, of 2 to 22%         by weight, preferably 4 to 20% by weight, in particular 8 to 18%         by weight, above all 10 to 16% by weight;     -   d) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by         weight, preferably 3 to 10% by weight, in particular 4 to 9% by         weight, above all 5 to 8% by weight;     -   e) an omega-3 fatty acid content of 1 to 6% by weight,         preferably 1.5 to 5% by weight, in particular 2 to 4.5% by         weight, above all 2.5 to 4% by weight;     -   f) a DHA content of 0.5 to 3% by weight, preferably 0.8 to 2.5%         by weight, in particular 1 to 2.5% by weight, above all 1.2 to         2.2% by weight, in particular 1.2 to 2.0% by weight.

The present invention preferably further provides the above-mentioned extrudates obtainable by oil coating and having preferably a water stability of at least 96%, in particular at least 97 or 98%.

Water stability was essentially determined as described by Baeverfjord et al. (2006; Aquaculture 261, 1335-1345), with slight modifications. 10 g samples of the extrudate (having a length and a diameter of 4 mm in each case) were introduced into metallic infusion baskets (Inox, Germany) having a diameter of 6.5 mm and a mesh size of 0.3 mm. The infusion baskets were subsequently introduced into a plastic trough containing water, and so the samples were completely covered with water. The trough was subsequently exposed for 30 minutes to a shake-agitation of 30 shake units per minute using the Multiorbital shaker PSU-20l (Biosan, Latvia). Thereafter, the samples were carefully dried with blotting paper and then weighed before and after they had been subjected to oven-drying at a temperature of 105° C. for 24 hours. Water stability was calculated as the difference in the dry weight of the sample before and after the incubation in water and specified in per cent of the dry weight of the sample used before the incubation with water.

According to the invention, the fat-containing component used may be, besides the biomass to be used according to the invention, fats, in particular oils, of both animal and plant origin. According to the invention, suitable fat-containing components are in particular vegetable oils, for example soya bean oil, rapeseed oil, sunflower seed oil, flaxseed oil or palm oil and mixtures thereof. In addition, fish oil may also optionally be used as fat-containing component in low amounts.

Preferably, a feedstuff according to the invention having an abrasion resistance of at least 96, 97 or 98% contains vegetable oils in an amount of 3 to 18% by weight, in particular 5 to 15% by weight, above all 7 to 13% by weight. As described above, the vegetable oil is in this connection preferably applied to the extrudate in a subsequent manner, in particular by vacuum coating.

According to the invention, the protein-containing component used may be, for example, soya protein, pea protein, wheat gluten or corn gluten and mixtures thereof.

The following examples may be employed as a protein-containing component which additionally contains fats: fish meal, krill meal, bivalve meal, squid meal or shrimp shells.

These are hereinafter subsumed under the term “marine meal”. In a preferred embodiment, a feedstuff according to the invention comprises marine meal, preferably fish meal, in an amount of 3 to 18% by weight, in particular 5 to 15% by weight, above all 7 to 13% by weight.

The carbohydrate-containing component used may be, for example, wheat meal, sunflower meal or soya meal and mixtures thereof.

When using feedstuffs according to the invention, in particular an oil-coated extrudate according to the invention, in animal farming, it became apparent that this especially promoted the growth of the animals and improved the stress level of the animals.

The present invention also further provides a method for farming animals, characterized in that they are administered with a feedstuff according to the invention.

In this connection, the present invention provides in particular a method for increasing the growth of animals, characterized in that they are administered with a feedstuff according to the invention.

The present invention further provides in particular similarly a method for increasing the fraction of omega-3 fatty acids, in particular DHA, in the muscle tissue of animals, characterized in that they are administered with a feedstuff according to the invention.

Preferably, in the process according to the invention, the feedstuff is administered at least every two days, preferably at least once daily.

The present invention further provides similarly the use of a feedstuff according to the invention for increasing growth in animals.

The present invention further provides likewise the use of a feedstuff according to the invention for increasing the fraction of omega-3 fatty acids in muscle tissue in animals.

The present invention further provides likewise the use of a feedstuff according to the invention for improving the physical condition of animals, in particular for improving the stress level of animals.

The present invention further provides likewise the use of a feedstuff according to the invention for allowing a stress-reduced farming of the animals.

The farmed animals fed with a feedstuff according to the invention are preferably poultry, pigs or cattle.

However, the farmed animals are especially preferably marine animals, especially preferably finfish or crustaceans. These include, in particular, carp, tilapia, catfish, tuna, salmon, trout, barramundi, bream, perch, cod, shrimps, lobster, crabs, prawns and crayfish. The farmed animals are especially preferably salmon. Preferred types of salmon in this context are the Atlantic salmon, red salmon, masu salmon, king salmon, keta salmon, coho salmon, Danube salmon, Pacific salmon and pink salmon.

The farmed animals may in particular also be fish which are subsequently processed into fish meal or fish oil. In this connection, the fish are preferably herring, pollack, menhaden, anchovies, capelin or cod. The fish meal or fish oil thus obtained, in turn, can be used in aquaculture for farming edible fish or crustaceans.

However, the farmed animals may also be small organisms which are used as feedstuff in aquaculture. These small organisms may take the form of, for example, nematodes, crustaceans or rotifers.

The farming of marine animals may take place in ponds, tanks, basins or else in segregated areas in the sea or in lakes, in particular in this case in cages or net pens. Farming may be used for farming the finished edible fish, but also may be used for farming fry which are subsequently released so as to restock the wild fish stocks.

In salmon farming, the fish are preferably first grown into smolts in freshwater tanks or artificial watercourses and then grown on in cages or net pens which float in the sea and which are preferably anchored in bays or fjords.

Accordingly, the feedstuff according to the invention is preferably a feedstuff for use in the farming of the above-mentioned animals.

WORKING EXAMPLES Example 1 Producing Biomass by Fermentation of Aurantiochytrium limacinum Sr21 in Media of Differing Sodium Sulphate Content

The cells were cultured for about 75 h in a feed process using a steel fermenter having a fermenter volume of 2 litres with a total starting mass of 712 g and an attained total final mass of 1.3-1.5 kg. During the process, a glucose solution (570 g/kg glucose) was metered in (fed-batch process)

The composition of the starting media was as follows:

Medium 1: 20 g/kg glucose; 4 g/kg yeast extract; 2 g/kg ammonium sulphate; 2.46 g/kg magnesium sulphate (heptahydrate); 0.45 g/kg potassium chloride; 4.5 g/kg potassium dihydrogen phosphate; 0.1 g/kg thiamine (HCl); 5 g/kg trace element solution.

Medium 2: As per medium 1 plus 8 g/kg sodium sulphate

Medium 3: As per medium 1 plus 12 g/kg sodium sulphate

Medium 4: As per medium 1 plus 16 g/kg sodium sulphate

The composition of the trace element solution was as follows: 35 g/kg hydrochloric acid (37%); 1.86 g/kg manganese chloride (tetrahydrate); 1.82 g/kg zinc sulphate (heptahydrate); 0.818 g/kg sodium EDTA; 0.29 g/kg boric acid; 0.24 g/kg sodium molybdate (dihydrate); 4.58 g/kg calcium chloride (dihydrate); 17.33 g/kg iron sulphate (heptahydrate); 0.15 g/kg copper chloride (dihydrate).

Culturing was carried out under the following conditions: Culture temperature 28° C.; aeration rate 0.5 vvm, stirrer speed 600-1950 rpm, control of pH in the growth phase at 4.5 using ammonia water (25% v/v). The following biomass densities were achieved: 100 g/l (medium 1), 111 g/l (medium 2), 114 g/l (medium 3), 116 g/l (medium 4).

After the culturing process, the fermentation broths were heated to 60° C. for 20 minutes in order to prevent further cellular activity.

Example 2 Determining the DHA Content of the Biomasses

After inactivation, the biomasses obtained were subjected to a fatty acid analysis. To this end, 0.2-0.5 ml of each fermentation broth was admixed with 1 ml of internal standard and topped up with 9 ml of a methanol/chloroform solution (1:2; v/v). The samples were treated for 10 min in an ultrasonic bath. Subsequently, the samples were concentrated to dryness under a nitrogen blanket at 50° C. in a thermal block. 2 ml of 0.5 N KOH were added to each of the residues of drying and incubated at 100° C. for 15 min. Subsequently, the samples were cooled down to room temperature, admixed with, in each case, 2 ml of 0.7 N HCl and 1 ml of boron trifluoride solution (14% BF3 in methanol) and incubated at 100° C. for a further 15 min. After cooling down to room temperature, the samples were each extracted with a mixture composed of 3 ml of water and 2 ml of heptane. After centrifugation for 1 min at 2000 rpm, 1 ml from each upper phase was transferred to a GC vial and analysed by gas chromatography.

The analysis revealed that all four biomasses contained a DHA fraction of more than 32% by weight with regard to the total amount of fatty acids present.

Example 3 Drying the Biomasses Obtained

The cooled-down biomass-containing fermentation broths having different contents of Na₂SO₄ according to Example 1 were each separately subjected to spray drying.

Spray drying was carried out in each case using a Büuchi mini spray dryer B-290 (diameter of nozzle tip: 0.7 mm; flow rate of spray air: 742 L/h; flow rate of aspirator: 35 m³/h; temperature of inlet air: 220° C.; temperature of outlet air: 80° C.).

Example 4 Determining the Sulphate and DHA Contents of the Spray-Dried Samples

The samples obtained by spray drying the fermentation broths having different contents of Na2SO4 were subjected to a sulphate or sulphur determination and a DHA concentration determination. DHA determination was carried out as described under Example 2. Sulphur content was determined in accordance with DIN EN ISO 11885.

TABLE 1 Analysis of spray-dried samples Starting medium of the fermentation broth used for spray drying Property Medium 1 Medium 2 Medium 3 Medium 4 Sulphur in 3.60 g/kg 7.72 g/kg 10.0 g/kg 11.0 g/kg accordance with DIN EN ISO 11885 DHA content 16.6% 15.6% 16.0% 16.0%

Example 4 Determining the Caking Tendency

The fermentation broths obtained after fermentation in media having different contents of sodium sulphate exhibited distinct differences in the spray drying process and the spray-dried material obtained exhibited varying caking tendency, the basis of this being released oil. The biomasses obtained by fermentation in media 3 and 4 showed a distinctly lower caking tendency than the biomasses obtained by fermentation in media 1 and 2. This is evidence of the increased cell stability of the cells in the biomasses concerned.

Example 5 Drying the Sulphate-Rich Biomass from Example 1 for the Purpose of Feedstuff Production

The biomass from Example 1 obtained in the sulphate-rich medium 4 was subjected to a two-stage drying process for the purpose of producing feedstuffs: Firstly, the fermentation broth was concentrated by evaporation to a dry mass of about 20% by weight. This was followed by spray drying of the concentrated fermentation broth using a Production Minor™ spray dryer (GEA NIRO) at a drying air inlet temperature of 340° C. By means of spray drying, a powder having a dry mass of more than 95% by weight was thus obtained.

Example 6 Producing a Feedstuff by Extrusion

The feedstuff mixtures shown in Table 3 were produced. Besides the biomass to be used according to the invention as per Example 5, two further commercially available Labyrinthulea biomasses and also fish oil as a currently still customary source of omega-3 fatty acids were tested for comparison.

The feedstuff mixtures were each produced by mixing of the components—with the exception of the oils—using a double-helix mixer (model 500L, TGC Extrusion, France). The mixtures thus obtained were then comminuted to particle sizes below 250 μm using a hammer mill (model SH1, Hosokawa-Alpine, Germany).

TABLE 2 Feedstuff compositions used in the extrusion process (data in % by weight) Ingredient M1 M2 M3 M4 Fish meal 10.00 10.00 10.00 10.00 Soya protein concentrate 23.10 23.20 23.10 20.27 Pea protein concentrate 15.00 15.00 15.00 15.00 Wheat gluten 9.90 9.90 9.90 9.90 Wheat meal 18.12 10.82 10.55 16.46 Fish oil 10.00 — — — Biomass from Example 1 — 16.00 — — Commercially available biomass 1 — — 16.74 — Commercially available biomass 2 — — — 13.52 Rape oil 10.00 11.00 11.00 11.00 Vitamin/mineral premix 1.00 1.00 1.00 1.00 DCP 2.00 2.00 2.00 2.00 Yttrium oxide 0.03 0.03 0.03 0.03 DL-Methionine 0.35 0.36 0.33 0.33 Aquavi Lys 0.17 0.35 0.08 0.19 TrypAmino 0.09 0.09 0.08 0.09 L-Histidine 0.24 0.25 0.19 0.21

For the extrusion process, use was made in each case of 140 kg per feedstuff. The extrusion process was carried out using a twin-screw extruder (CLEXTRAL BC45) having a screw diameter of 55.5 mm and a maximum flow rate of 90-100 kg/h. Pellets of 4.0 mm in size (diameter and length) were extruded. To this end, the extruder was equipped with a high-speed cutter in order to convert the product to the intended pellet size.

Various extrusion parameters were then tested in order to find out under what extrusion conditions it is possible to obtain an optimal oil load capacity of the extrudate obtained. In this connection, it became apparent that, surprisingly, an optimal oil load capacity can be achieved with a very low energy input. In this connection, the energy input was distinctly lower than when using fish oil. Furthermore, the optimal energy input in the case of an algae biomass to be preferably used according to the invention was again distinctly lower than in the case of commercially available algae biomasses. The results are shown in Table 3.

TABLE 3 Energy inputs relating to producing pellets having the desired oil load capacity Barrel 1 Barrel 2 Rotational Amount of Temp Temp Feeder rate speed water Current SME Diet (° C.) (° C.) (kg/h) (rpm) (0-10) (A) (Wh/kg) M1 31 116-118  112 215 9 11 34.6 M2 32 98-104 141 253 5 7 20.6 M3 32 97-102 136 255 5 8 24.6 M4 31 99-107 133 253 5 8 24.9

In this connection, the variable “SME” is the specific mechanical energy. This is calculated as follows:

${{SME}\mspace{14mu} \left( {{Wh}\text{/}{kg}} \right)} = \frac{{UI\cos}\; \Phi \frac{{Test}\mspace{14mu} {SS}}{{Max}\mspace{14mu} {SS}}}{Qs}$

where

U: operating voltage of the motor (here 460 V)

I: current of the motor (A)

cos φ: theoretical performance of the extruder motor (here 0.95)

Test SS: test speed (rpm) of the rotating screws

Max SS: maximum speed (267 rpm) of the rotating screws

Qs: inlet flow rate of the mash (kg/h)

After extrusion, the extrudate was dried in a vibrating fluidized bed dryer (model DR100, TGC Extrusion, France).

This was followed, after the extrudate had cooled down, by an oil coating process by means of vacuum coating (vacuum coater PG-10VCLAB, Dinnisen, the Netherlands).

Example 7 Ascertaining the Abrasion Resistance and Water Stability of the Feedstuffs from Example 6

Abrasion resistance was ascertained as follows: Before being loaded with oil, the dried extrusion product was exposed to a mechanical load using the Holmen pellet tester (Borregaard Lignotech, Hull, UK). Before carrying out the test, the samples were screened in order to remove any adherent fine particles. The processed samples (100 g) were subsequently introduced into the pellet tester using a 2.5 mm filter screen. The pellets were subsequently conveyed through a pipe having right-angled pipe bends at high air velocity for 30 seconds. Subsequently, abrasion was determined by weighing. Abrasion resistance was specified as PDI (Pellet Durability Index), defined as the amount in per cent of sample remaining in the filter screen. The test was carried out with three samples and then the mean was determined.

Water stability was carried out using the oil-loaded samples. The method was essentially carried out as described by Baeverfjord et al. (2006; Aquaculture 261, 1335-1345), with slight modifications. 10 g samples were introduced into metallic infusion baskets having a mesh size of 0.3 mm. The infusion baskets were subsequently introduced into a plastic trough containing water, and so the samples were completely covered with water. The trough was subsequently exposed for 30 minutes to a shake-agitation of 30 shake units per minute. Thereafter, the samples were carefully dried with blotting paper and then weighed before and after they had been subjected to oven-drying at a temperature of 105° C. for 24 hours. Water stability was calculated as the difference in the dry weight of the sample before and after the incubation in water and specified in per cent of the dry weight of the sample used before the incubation with water.

The results are shown in Table 4 below.

Sample M1 M2 M3 M4 Abrasion 90.0 93.3 88.3 85.2 resistance [%] Water stability [%] 95.7 98.5 93.8 90.2

It can be seen that a feedstuff according to the invention which contains a biomass according to the invention has a distinctly higher abrasion resistance and water stability than feedstuffs which contain a commercially available Labyrinthulea biomass or fish oil as a source of omega-3 fatty acids.

Example 8 Producing Feedstuffs for Feeding Experiments

Feedstuffs each containing 42.5% by weight of total protein and 24% by weight of total lipid, based on the dry mass, and having a pellet size of 3 mm were produced by extrusion of the biomass from Example 5.

Three different feedstuff formulations in total were produced (Diet 1, 2 and 3). The control formulation “Diet 1” contained 11.0% by weight of fish oil. In the formulation “Diet 2”, the fish oil was partly (about 50%) replaced by Aurantiochytrium biomass, this being done by adding 9.1% by weight of biomass and, for that reason, reducing the amount of fish oil to 5.5% by weight. In the formulation “Diet 3”, the fish oil was completely replaced by Aurantiochytrium biomass, this being done by adding 16% by weight of biomass and, at the same time, increasing the amount of rape oil from 8.2 to 9.9% by weight. Differences in the total weight were balanced out by the amount of wheat added.

The individual components of the feedstuff are shown in the table below.

TABLE 5 Formulations used for farming Components (g kg⁻¹) Diet 1 Diet 2 Diet 3 Aurantiochytrium biomass 0.0 91.6 160.0 SPC 229.0 229.0 229.0 Fish meal 150.0 150.0 150.0 Wheat 147.6 111.0 80.5 Fish oil 110.0 55.0 0.0 Wheat gluten 100.0 100.0 100.0 Pea protein concentrate 100.0 100.0 100.0 Rape oil 82.0 82.0 99.1 Monosodium phosphate 20.0 20.0 20.0 Vitamin mixture 20.0 20.0 20.0 Soya lecithin 10.0 10.0 10.0 L-Lysine (50% by weight) 10.0 10.0 10.0 Betafine 9.4 9.4 9.4 Mineral mixture 5.2 5.2 5.2 L-Histidine (98% by 4.2 4.2 4.2 weight) DL-Methionine (99% by 2.0 2.0 2.0 weight) Carop. Pink (10% by 0.50 0.50 0.50 weight) Yttrium Oxide 0.10 0.10 0.10

The individual components were—with the exception of the oils—mixed intimately with each other and then an extrudate was produced using a twin-screw extruder (Wenger Tex. 52, Wenger, USA) through use of an outlet nozzle having a diameter of 2 mm. The extrudates were dried for about 1 hour in a carousel dryer (Paul Klöckner, Verfahrenstechnik GmbH, Germany) at 65° C. to a water content of 7 to 8% by weight. The extrudates were then dried overnight at room temperature before the oils were applied by vacuum coating (Dinnissen, Sevenum, the Netherlands).

Example 9 Feeding Experiments Using the Formulations from Example 8

The feeding experiments were carried out by feeding each of these formulations for a total of 12 weeks to each of three tanks containing smolts having a mean weight of 83.6 g and a total salmon weight of 4 kg per tank.

Over this period, the total salmon weight per tank increased from 4 kg to 15-17 kg per tank. In this connection, the fish consumed 8 to 11 kg of feed per tank, corresponding to a feed conversion rate (FCR) of 0.8 to 0.9 kg of feed per kg of fish.

The results of the feeding experiments are shown in the table below.

TABLE 6 Diet-dependent fish weight gain Diet Final weight [g] 1 331 2 362 3 339

Altogether, it was established that it was possible to achieve an increase in salmon growth both in the case of complete and in the case of partial replacement of the fish oil by an Aurantiochytrium biomass according to the invention.

Interestingly, partial replacement of the fish oil by the Aurantiochytrium biomass achieved a higher salmon growth than complete replacement by the Aurantiochytrium biomass.

In this connection, it was established that the fish fed with the control formulation Diet 1, having a mean final weight of 331 g, had a distinctly lower final weight than the fish fed with the formulations Diet 1 or 2. In this connection, the fish fed with the formulation Diet 2 performed the best: they achieved a distinctly increased mean final weight of 362 g.

Example 10 Fatty Acid Utilization by the Fish

Fatty acid utilization was ascertained by lipid detection using the Bligh & Dryer extraction method and subsequent fatty acid analysis in accordance with AOCS Ce 1b-89. Both muscle samples and total salmon samples were analysed. In this connection, the results shown in the tables below were obtained (displayed in each table is the amount of ascertained fats at the start and end of the diet in grams, based in each case on 100 g of total fat).

TABLE 7 Diet-dependent fatty acid profile of salmon muscle samples Diet PUFAs Omega-3 fatty acids DHA Start 41.6 32.7 22.1 1 31.8 19.0 10.1 2 35.3 21.7 14.2 3 38.0 22.8 16.4

TABLE 8 Diet-dependent fatty acid profile of total salmon samples Diet PUFAs Omega-3 fatty acids DHA Start 32.5 22.4 12.5 1 29.9 17.2 9.0 2 32.6 18.8 11.5 3 35.2 19.6 13.1

It can be observed that it was already possible to achieve a distinct increase in the content of PUFAs, omega-3 fatty acids and DHA in the case of partial replacement of the fish oil by an Aurantiochytrium biomass according to the invention. In the case of complete replacement of the fish oil by the Aurantiochytrium biomass, the increase in the content of PUFAs is accordingly higher.

Example 11 Determining the Fat Content in Salmon Liver

Each of 3 smolts were fed for 9 weeks in each case with the different formulations Diet 1, 2 and 3 and the livers of the salmons were subsequently removed for determination of the fat content. Fat was extracted according to the method by Folch (1957; J. Biol. Chem., 226 (1), 497-509). Fat content was then determined by a gravimetric method.

It became apparent that it was possible to significantly reduce the fat content in the liver from 8% by weight to 4-5% by weight by virtue of the presence of the biomass according to the invention in comparison with feeding without the biomass.

Fat deposition in the liver is considered to be a sign of an imbalance in food metabolism and, in particular, also an indication of oxidative stress. The distinct reduction in the proportion of fat in the liver is thus a clear indication of the reduction of stress and thus of the improvement in the physical condition of the salmon. 

1-15. (canceled)
 16. A PUFA-containing biomass, comprising a sulphate content, based on the dry biomass, of 25 to 60 g/kg, and wherein the biomass contains cells of the taxon Labyrinthulomycetes.
 17. The PUFA-containing biomass of claim 16, wherein said biomass has a sulphate content, based on the dry biomass, of 25 to 40 g/kg.
 18. The PUFA-containing biomass of claim 16, wherein said biomass has a sulphate content, based on the dry mass, of 25 to 30 g/kg.
 19. The PUFA-containing biomass of claim 16, wherein the cells of the taxon Labyrinthulomycetes (Labyrinthulea, slime nets) are of the family Thraustochytriaceae.
 20. The PUFA-containing biomass of claim 19, wherein the cells are of a genus selected from the group consisting of: Althomia; Aplanochytrium; Elnia; Japonochytrium; Schizochytrium; Thraustochytrium; Aurantiochytrium; Oblongichytrium; and Ulkenia.
 21. The PUFA-containing biomass of claim 20, wherein the cells are of the species Aurantiochytrium limacinum.
 22. A feedstuff, comprising a PUFA-containing biomass, wherein said PUFA-containing biomass has a sulphate content, based on the dry mass, of 25 to 60 g/kg, and wherein the biomass contains cells of the taxon Labyrinthulomycetes.
 23. The feedstuff of claim 22, comprising the following properties: a) a total protein content of 30 to 60% by weight; b) a total fat content of 15 to 35% by weight; c) a total starch content of at most 25% by weight; d) a content of biomass of 2 to 22% by weight.
 24. The feedstuff of claim 23, wherein the biomass comprises cells of a genus selected from the group consisting of: Althomia; Aplanochytrium; Elnia; Japono-chytrium; Schizochytrium; Thraustochytrium; Aurantiochytrium; Oblongichytrium; and Ulkenia.
 25. The feedstuff of claim 24, wherein the biomass comprises cells of the species Aurantiochytrium limacinum.
 26. The feedstuff of claim 23, comprising one or more of the following properties: e) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by weight; f) an omega-3 fatty acid content of 1 to 6% by weight; g) a DHA content of 0.5 to 3% by weight.
 27. The feedstuff of claim 23, comprising at least two of the following properties: e) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by weight; f) an omega-3 fatty acid content of 1 to 6% by weight; g) a DHA content of 0.5 to 3% by weight.
 28. The feedstuff of claim 23, comprising all of the following properties: g) a polyunsaturated fatty acid (PUFA) content of 2 to 12% by weight; f) an omega-3 fatty acid content of 1 to 6% by weight; g) a DHA content of 0.5 to 3% by weight.
 29. The feedstuff of claim 22, comprising the following properties: a) a total protein content of 40 to 50% by weight; b) a total fat content of 20 to 30% by weight; c) a total starch content of 5 to 15% by weight; d) a content of Thraustochytriaceae biomass of 10 to 16% by weight.
 30. The feedstuff of claim 29, comprising one or more of the following properties: e) a polyunsaturated fatty acid (PUFA) content of 3 to 10% by weight; f) an omega-3 fatty acid content of 2 to 4.5% by weight; g) a DHA content of 1.2 to 2.2%.
 31. The feedstuff of claim 29, comprising at least two of the following properties: e) a polyunsaturated fatty acid (PUFA) content of 3 to 10% by weight; f) an omega-3 fatty acid content of 2 to 4.5% by weight; g) a DHA content of 1.2 to 2.2%.
 32. The feedstuff of claim 29, comprising all of the following properties: e) a polyunsaturated fatty acid (PUFA) content of 3 to 10% by weight; f) an omega-3 fatty acid content of 2 to 4.5% by weight; g) a DHA content of 1.2 to 2.2%.
 33. The feedstuff of claim 32, wherein the biomass comprises cells of a genus selected from the group consisting of: Althomia; Aplanochytrium; Elnia; Japono-chytrium; Schizochytrium; Thraustochytrium; Aurantiochytrium; Oblongichytrium; and Ulkenia.
 34. The feedstuff of claim 32, wherein the biomass comprises cells of the species Aurantiochytrium limacinum.
 35. A method for farming animals, comprising feeding said animals the feedstuff of claim
 22. 